The present invention is directed to a steam sterilization indicator, and more particularly, to an indicator for monitoring the extent of exposure of a device to steam as well as whether or not exposure to steam has occurred.
Steam sterilization indicators are well known in the art as exemplified by U.S. Pat. Nos. 3,981,683 and 4,448,548. These indicators generally include a backing strip of a dimensionally stable material such as aluminum foil or the like. A fusible material usually formed in tablet form is deposited on the backing strip. A wick is attached to the backing strip with one end of the wick in intimate contact with the fusible tablet. A transparent plastic covers the tablet and the wick and is adhered to the backing strip. The normal melting point of the fusible tablet is depressed in the presence of saturated steam and upon exposure to saturated steam over a predescribed time period melts. The tablet melt is absorbed by the wick producing a visual indication of the device's integration of the exposure time and temperature in the presence of saturated steam.
However, such steam sterilization indicators are often utilized deep within fabric packs incorporating towels or the like. Accordingly, these pack/indicator combinations frequently suffer from the disadvantage that in order to determine whether the pack has actually been exposed to steam during a sterilization cycle, the pack must be unravelled. (destroying the integrity of the pack) to determine whether the fusible material has melted at all possibly indicating that exposure to a sterilizing amount of steam has occurred. If there is no indication of exposure to steam, then the pack must be repackaged resulting in inefficiencies requiring the waste of time of test personnel. Additionally, the prior art device lends itself to false readings. If in fact the device was exposed to steam, and the device was not exposed to steam of a high enough temperature or for a long enough period to melt the fusible material, when the pack is unwrapped, it will appear as if the pack has never been exposed to steam, providing a false reading.
Accordingly, a steam sterilization indicator which indicates exposure to steam without the necessity of unwrapping the pack is desired with attendant marked advantages.